gold/gold.cc

   1 // gold.cc -- main linker functions
   2
   3 // Copyright (C) 2006-2015 Free Software Foundation, Inc.
   4 // Written by Ian Lance Taylor <iant@google.com>.
   5
   6 // This file is part of gold.
   7
   8 // This program is free software; you can redistribute it and/or modify
   9 // it under the terms of the GNU General Public License as published by
  10 // the Free Software Foundation; either version 3 of the License, or
  11 // (at your option) any later version.
  12
  13 // This program is distributed in the hope that it will be useful,
  14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 // GNU General Public License for more details.
  17
  18 // You should have received a copy of the GNU General Public License
  19 // along with this program; if not, write to the Free Software
  20 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
  21 // MA 02110-1301, USA.
  22
  23 #include "gold.h"
  24
  25 #include <cstdlib>
  26 #include <cstdio>
  27 #include <cstring>
  28 #include <unistd.h>
  29 #include <algorithm>
  30 #include "libiberty.h"
  31
  32 #include "options.h"
  33 #include "target-select.h"
  34 #include "debug.h"
  35 #include "workqueue.h"
  36 #include "dirsearch.h"
  37 #include "readsyms.h"
  38 #include "symtab.h"
  39 #include "common.h"
  40 #include "object.h"
  41 #include "layout.h"
  42 #include "reloc.h"
  43 #include "defstd.h"
  44 #include "plugin.h"
  45 #include "gc.h"
  46 #include "icf.h"
  47 #include "incremental.h"
  48 #include "timer.h"
  49
  50 namespace gold
  51 {
  52
  53 class Object;
  54
  55 const char* program_name;
  56
  57 static Task*
  58 process_incremental_input(Incremental_binary*, unsigned int, Input_objects*,
  59                           Symbol_table*, Layout*, Dirsearch*, Mapfile*,
  60                           Task_token*, Task_token*);
  61
  62 void
  63 gold_exit(Exit_status status)
  64 {
  65   if (parameters != NULL
  66       && parameters->options_valid()
  67       && parameters->options().has_plugins())
  68     parameters->options().plugins()->cleanup();
  69   if (status != GOLD_OK && parameters != NULL && parameters->options_valid())
  70     unlink_if_ordinary(parameters->options().output_file_name());
  71   exit(status);
  72 }
  73
  74 void
  75 gold_nomem()
  76 {
  77   // We are out of memory, so try hard to print a reasonable message.
  78   // Note that we don't try to translate this message, since the
  79   // translation process itself will require memory.
  80
  81   // LEN only exists to avoid a pointless warning when write is
  82   // declared with warn_use_result, as when compiling with
  83   // -D_USE_FORTIFY on GNU/Linux.  Casting to void does not appear to
  84   // work, at least not with gcc 4.3.0.
  85
  86   ssize_t len = write(2, program_name, strlen(program_name));
  87   if (len >= 0)
  88     {
  89       const char* const s = ": out of memory\n";
  90       len = write(2, s, strlen(s));
  91     }
  92   gold_exit(GOLD_ERR);
  93 }
  94
  95 // Handle an unreachable case.
  96
  97 void
  98 do_gold_unreachable(const char* filename, int lineno, const char* function)
  99 {
 100   fprintf(stderr, _("%s: internal error in %s, at %s:%d\n"),
 101           program_name, function, filename, lineno);
 102   gold_exit(GOLD_ERR);
 103 }
 104
 105 // This class arranges to run the functions done in the middle of the
 106 // link.  It is just a closure.
 107
 108 class Middle_runner : public Task_function_runner
 109 {
 110  public:
 111   Middle_runner(const General_options& options,
 112                 const Input_objects* input_objects,
 113                 Symbol_table* symtab,
 114                 Layout* layout, Mapfile* mapfile)
 115     : options_(options), input_objects_(input_objects), symtab_(symtab),
 116       layout_(layout), mapfile_(mapfile)
 117   { }
 118
 119   void
 120   run(Workqueue*, const Task*);
 121
 122  private:
 123   const General_options& options_;
 124   const Input_objects* input_objects_;
 125   Symbol_table* symtab_;
 126   Layout* layout_;
 127   Mapfile* mapfile_;
 128 };
 129
 130 void
 131 Middle_runner::run(Workqueue* workqueue, const Task* task)
 132 {
 133   queue_middle_tasks(this->options_, task, this->input_objects_, this->symtab_,
 134                      this->layout_, workqueue, this->mapfile_);
 135 }
 136
 137 // This class arranges the tasks to process the relocs for garbage collection.
 138
 139 class Gc_runner : public Task_function_runner
 140 {
 141   public:
 142    Gc_runner(const General_options& options,
 143              const Input_objects* input_objects,
 144              Symbol_table* symtab,
 145              Layout* layout, Mapfile* mapfile)
 146     : options_(options), input_objects_(input_objects), symtab_(symtab),
 147       layout_(layout), mapfile_(mapfile)
 148    { }
 149
 150   void
 151   run(Workqueue*, const Task*);
 152
 153  private:
 154   const General_options& options_;
 155   const Input_objects* input_objects_;
 156   Symbol_table* symtab_;
 157   Layout* layout_;
 158   Mapfile* mapfile_;
 159 };
 160
 161 void
 162 Gc_runner::run(Workqueue* workqueue, const Task* task)
 163 {
 164   queue_middle_gc_tasks(this->options_, task, this->input_objects_,
 165                         this->symtab_, this->layout_, workqueue,
 166                         this->mapfile_);
 167 }
 168
 169 // Queue up the initial set of tasks for this link job.
 170
 171 void
 172 queue_initial_tasks(const General_options& options,
 173                     Dirsearch& search_path,
 174                     const Command_line& cmdline,
 175                     Workqueue* workqueue, Input_objects* input_objects,
 176                     Symbol_table* symtab, Layout* layout, Mapfile* mapfile)
 177 {
 178   if (cmdline.begin() == cmdline.end())
 179     {
 180       bool is_ok = false;
 181       if (options.printed_version())
 182         is_ok = true;
 183       if (options.print_output_format())
 184         {
 185           print_output_format();
 186           is_ok = true;
 187         }
 188       if (is_ok)
 189         gold_exit(GOLD_OK);
 190       gold_fatal(_("no input files"));
 191     }
 192
 193   int thread_count = options.thread_count_initial();
 194   if (thread_count == 0)
 195     thread_count = cmdline.number_of_input_files();
 196   workqueue->set_thread_count(thread_count);
 197
 198   // For incremental links, the base output file.
 199   Incremental_binary* ibase = NULL;
 200
 201   if (parameters->incremental_update())
 202     {
 203       Output_file* of = new Output_file(options.output_file_name());
 204       if (of->open_base_file(options.incremental_base(), true))
 205         {
 206           ibase = open_incremental_binary(of);
 207           if (ibase != NULL
 208               && ibase->check_inputs(cmdline, layout->incremental_inputs()))
 209             ibase->init_layout(layout);
 210           else
 211             {
 212               delete ibase;
 213               ibase = NULL;
 214               of->close();
 215             }
 216         }
 217       if (ibase == NULL)
 218         {
 219           if (set_parameters_incremental_full())
 220             gold_info(_("linking with --incremental-full"));
 221           else
 222             gold_fallback(_("restart link with --incremental-full"));
 223         }
 224     }
 225
 226   // Read the input files.  We have to add the symbols to the symbol
 227   // table in order.  We do this by creating a separate blocker for
 228   // each input file.  We associate the blocker with the following
 229   // input file, to give us a convenient place to delete it.
 230   Task_token* this_blocker = NULL;
 231   if (ibase == NULL)
 232     {
 233       // Normal link.  Queue a Read_symbols task for each input file
 234       // on the command line.
 235       for (Command_line::const_iterator p = cmdline.begin();
 236            p != cmdline.end();
 237            ++p)
 238         {
 239           Task_token* next_blocker = new Task_token(true);
 240           next_blocker->add_blocker();
 241           workqueue->queue(new Read_symbols(input_objects, symtab, layout,
 242                                             &search_path, 0, mapfile, &*p, NULL,
 243                                             NULL, this_blocker, next_blocker));
 244           this_blocker = next_blocker;
 245         }
 246     }
 247   else
 248     {
 249       // Incremental update link.  Process the list of input files
 250       // stored in the base file, and queue a task for each file:
 251       // a Read_symbols task for a changed file, and an Add_symbols task
 252       // for an unchanged file.  We need to mark all the space used by
 253       // unchanged files before we can start any tasks running.
 254       unsigned int input_file_count = ibase->input_file_count();
 255       std::vector<Task*> tasks;
 256       tasks.reserve(input_file_count);
 257       for (unsigned int i = 0; i < input_file_count; ++i)
 258         {
 259           Task_token* next_blocker = new Task_token(true);
 260           next_blocker->add_blocker();
 261           Task* t = process_incremental_input(ibase, i, input_objects, symtab,
 262                                               layout, &search_path, mapfile,
 263                                               this_blocker, next_blocker);
 264           tasks.push_back(t);
 265           this_blocker = next_blocker;
 266         }
 267       // Now we can queue the tasks.
 268       for (unsigned int i = 0; i < tasks.size(); i++)
 269         workqueue->queue(tasks[i]);
 270     }
 271
 272   if (options.has_plugins())
 273     {
 274       Task_token* next_blocker = new Task_token(true);
 275       next_blocker->add_blocker();
 276       workqueue->queue(new Plugin_hook(options, input_objects, symtab, layout,
 277                                        &search_path, mapfile, this_blocker,
 278                                        next_blocker));
 279       this_blocker = next_blocker;
 280     }
 281
 282   if (options.relocatable()
 283       && (options.gc_sections() || options.icf_enabled()))
 284     gold_error(_("cannot mix -r with --gc-sections or --icf"));
 285
 286   if (options.gc_sections() || options.icf_enabled())
 287     {
 288       workqueue->queue(new Task_function(new Gc_runner(options,
 289                                                        input_objects,
 290                                                        symtab,
 291                                                        layout,
 292                                                        mapfile),
 293                                          this_blocker,
 294                                          "Task_function Gc_runner"));
 295     }
 296   else
 297     {
 298       workqueue->queue(new Task_function(new Middle_runner(options,
 299                                                            input_objects,
 300                                                            symtab,
 301                                                            layout,
 302                                                            mapfile),
 303                                          this_blocker,
 304                                          "Task_function Middle_runner"));
 305     }
 306 }
 307
 308 // Process an incremental input file: if it is unchanged from the previous
 309 // link, return a task to add its symbols from the base file's incremental
 310 // info; if it has changed, return a normal Read_symbols task.  We create a
 311 // task for every input file, if only to report the file for rebuilding the
 312 // incremental info.
 313
 314 static Task*
 315 process_incremental_input(Incremental_binary* ibase,
 316                           unsigned int input_file_index,
 317                           Input_objects* input_objects,
 318                           Symbol_table* symtab,
 319                           Layout* layout,
 320                           Dirsearch* search_path,
 321                           Mapfile* mapfile,
 322                           Task_token* this_blocker,
 323                           Task_token* next_blocker)
 324 {
 325   const Incremental_binary::Input_reader* input_reader =
 326       ibase->get_input_reader(input_file_index);
 327   Incremental_input_type input_type = input_reader->type();
 328
 329   // Get the input argument corresponding to this input file, matching on
 330   // the argument serial number.  If the input file cannot be matched
 331   // to an existing input argument, synthesize a new one.
 332   const Input_argument* input_argument =
 333       ibase->get_input_argument(input_file_index);
 334   if (input_argument == NULL)
 335     {
 336       Input_file_argument file(input_reader->filename(),
 337                                Input_file_argument::INPUT_FILE_TYPE_FILE,
 338                                "", false, parameters->options());
 339       Input_argument* arg = new Input_argument(file);
 340       arg->set_script_info(ibase->get_script_info(input_file_index));
 341       input_argument = arg;
 342     }
 343
 344   gold_debug(DEBUG_INCREMENTAL, "Incremental object: %s, type %d",
 345              input_reader->filename(), input_type);
 346
 347   if (input_type == INCREMENTAL_INPUT_SCRIPT)
 348     {
 349       // Incremental_binary::check_inputs should have cancelled the
 350       // incremental update if the script has changed.
 351       gold_assert(!ibase->file_has_changed(input_file_index));
 352       return new Check_script(layout, ibase, input_file_index, input_reader,
 353                               this_blocker, next_blocker);
 354     }
 355
 356   if (input_type == INCREMENTAL_INPUT_ARCHIVE)
 357     {
 358       Incremental_library* lib = ibase->get_library(input_file_index);
 359       gold_assert(lib != NULL);
 360       if (lib->filename() == "/group/"
 361           || !ibase->file_has_changed(input_file_index))
 362         {
 363           // Queue a task to check that no references have been added to any
 364           // of the library's unused symbols.
 365           return new Check_library(symtab, layout, ibase, input_file_index,
 366                                    input_reader, this_blocker, next_blocker);
 367         }
 368       else
 369         {
 370           // Queue a Read_symbols task to process the archive normally.
 371           return new Read_symbols(input_objects, symtab, layout, search_path,
 372                                   0, mapfile, input_argument, NULL, NULL,
 373                                   this_blocker, next_blocker);
 374         }
 375     }
 376
 377   if (input_type == INCREMENTAL_INPUT_ARCHIVE_MEMBER)
 378     {
 379       // For archive members, check the timestamp of the containing archive.
 380       Incremental_library* lib = ibase->get_library(input_file_index);
 381       gold_assert(lib != NULL);
 382       // Process members of a --start-lib/--end-lib group as normal objects.
 383       if (lib->filename() != "/group/")
 384         {
 385           if (ibase->file_has_changed(lib->input_file_index()))
 386             {
 387               return new Read_member(input_objects, symtab, layout, mapfile,
 388                                      input_reader, this_blocker, next_blocker);
 389             }
 390           else
 391             {
 392               // The previous contributions from this file will be kept.
 393               // Mark the pieces of output sections contributed by this
 394               // object.
 395               ibase->reserve_layout(input_file_index);
 396               Object* obj = make_sized_incremental_object(ibase,
 397                                                           input_file_index,
 398                                                           input_type,
 399                                                           input_reader);
 400               return new Add_symbols(input_objects, symtab, layout,
 401                                      search_path, 0, mapfile, input_argument,
 402                                      obj, lib, NULL, this_blocker,
 403                                      next_blocker);
 404             }
 405         }
 406     }
 407
 408   // Normal object file or shared library.  Check if the file has changed
 409   // since the last incremental link.
 410   if (ibase->file_has_changed(input_file_index))
 411     {
 412       return new Read_symbols(input_objects, symtab, layout, search_path, 0,
 413                               mapfile, input_argument, NULL, NULL,
 414                               this_blocker, next_blocker);
 415     }
 416   else
 417     {
 418       // The previous contributions from this file will be kept.
 419       // Mark the pieces of output sections contributed by this object.
 420       ibase->reserve_layout(input_file_index);
 421       Object* obj = make_sized_incremental_object(ibase,
 422                                                   input_file_index,
 423                                                   input_type,
 424                                                   input_reader);
 425       return new Add_symbols(input_objects, symtab, layout, search_path, 0,
 426                              mapfile, input_argument, obj, NULL, NULL,
 427                              this_blocker, next_blocker);
 428     }
 429 }
 430
 431 // Queue up a set of tasks to be done before queueing the middle set
 432 // of tasks.  This is only necessary when garbage collection
 433 // (--gc-sections) of unused sections is desired.  The relocs are read
 434 // and processed here early to determine the garbage sections before the
 435 // relocs can be scanned in later tasks.
 436
 437 void
 438 queue_middle_gc_tasks(const General_options& options,
 439                       const Task* ,
 440                       const Input_objects* input_objects,
 441                       Symbol_table* symtab,
 442                       Layout* layout,
 443                       Workqueue* workqueue,
 444                       Mapfile* mapfile)
 445 {
 446   // Read_relocs for all the objects must be done and processed to find
 447   // unused sections before any scanning of the relocs can take place.
 448   Task_token* this_blocker = NULL;
 449   for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 450        p != input_objects->relobj_end();
 451        ++p)
 452     {
 453       Task_token* next_blocker = new Task_token(true);
 454       next_blocker->add_blocker();
 455       workqueue->queue(new Read_relocs(symtab, layout, *p, this_blocker,
 456                                        next_blocker));
 457       this_blocker = next_blocker;
 458     }
 459
 460   // If we are given only archives in input, we have no regular
 461   // objects and THIS_BLOCKER is NULL here.  Create a dummy
 462   // blocker here so that we can run the middle tasks immediately.
 463   if (this_blocker == NULL)
 464     {
 465       gold_assert(input_objects->number_of_relobjs() == 0);
 466       this_blocker = new Task_token(true);
 467     }
 468
 469   workqueue->queue(new Task_function(new Middle_runner(options,
 470                                                        input_objects,
 471                                                        symtab,
 472                                                        layout,
 473                                                        mapfile),
 474                                      this_blocker,
 475                                      "Task_function Middle_runner"));
 476 }
 477
 478 // Queue up the middle set of tasks.  These are the tasks which run
 479 // after all the input objects have been found and all the symbols
 480 // have been read, but before we lay out the output file.
 481
 482 void
 483 queue_middle_tasks(const General_options& options,
 484                    const Task* task,
 485                    const Input_objects* input_objects,
 486                    Symbol_table* symtab,
 487                    Layout* layout,
 488                    Workqueue* workqueue,
 489                    Mapfile* mapfile)
 490 {
 491   Timer* timer = parameters->timer();
 492   if (timer != NULL)
 493     timer->stamp(0);
 494
 495   // Add any symbols named with -u options to the symbol table.
 496   symtab->add_undefined_symbols_from_command_line(layout);
 497
 498   // If garbage collection was chosen, relocs have been read and processed
 499   // at this point by pre_middle_tasks.  Layout can then be done for all
 500   // objects.
 501   if (parameters->options().gc_sections())
 502     {
 503       // Find the start symbol if any.
 504       Symbol* sym = symtab->lookup(parameters->entry());
 505       if (sym != NULL)
 506         symtab->gc_mark_symbol(sym);
 507       sym = symtab->lookup(parameters->options().init());
 508       if (sym != NULL && sym->is_defined() && !sym->is_from_dynobj())
 509         symtab->gc_mark_symbol(sym);
 510       sym = symtab->lookup(parameters->options().fini());
 511       if (sym != NULL && sym->is_defined() && !sym->is_from_dynobj())
 512         symtab->gc_mark_symbol(sym);
 513       // Symbols named with -u should not be considered garbage.
 514       symtab->gc_mark_undef_symbols(layout);
 515       gold_assert(symtab->gc() != NULL);
 516       // Do a transitive closure on all references to determine the worklist.
 517       symtab->gc()->do_transitive_closure();
 518     }
 519
 520   // If identical code folding (--icf) is chosen it makes sense to do it
 521   // only after garbage collection (--gc-sections) as we do not want to
 522   // be folding sections that will be garbage.
 523   if (parameters->options().icf_enabled())
 524     {
 525       symtab->icf()->find_identical_sections(input_objects, symtab);
 526     }
 527
 528   // Call Object::layout for the second time to determine the
 529   // output_sections for all referenced input sections.  When
 530   // --gc-sections or --icf is turned on, or when certain input
 531   // sections have to be mapped to unique segments, Object::layout
 532   // is called twice.  It is called the first time when symbols
 533   // are added.
 534   if (parameters->options().gc_sections()
 535       || parameters->options().icf_enabled()
 536       || layout->is_unique_segment_for_sections_specified())
 537     {
 538       for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 539            p != input_objects->relobj_end();
 540            ++p)
 541         {
 542           Task_lock_obj<Object> tlo(task, *p);
 543           (*p)->layout(symtab, layout, NULL);
 544         }
 545     }
 546
 547   // Layout deferred objects due to plugins.
 548   if (parameters->options().has_plugins())
 549     {
 550       Plugin_manager* plugins = parameters->options().plugins();
 551       gold_assert(plugins != NULL);
 552       plugins->layout_deferred_objects();
 553     }
 554
 555   /* If plugins have specified a section order, re-arrange input sections
 556      according to a specified section order.  If --section-ordering-file is
 557      also specified, do not do anything here.  */
 558   if (parameters->options().has_plugins()
 559       && layout->is_section_ordering_specified()
 560       && !parameters->options().section_ordering_file ())
 561     {
 562       for (Layout::Section_list::const_iterator p
 563              = layout->section_list().begin();
 564            p != layout->section_list().end();
 565            ++p)
 566         (*p)->update_section_layout(layout->get_section_order_map());
 567     }
 568
 569   if (parameters->options().gc_sections()
 570       || parameters->options().icf_enabled())
 571     {
 572       for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 573            p != input_objects->relobj_end();
 574            ++p)
 575         {
 576           // Update the value of output_section stored in rd.
 577           Read_relocs_data* rd = (*p)->get_relocs_data();
 578           for (Read_relocs_data::Relocs_list::iterator q = rd->relocs.begin();
 579                q != rd->relocs.end();
 580                ++q)
 581             {
 582               q->output_section = (*p)->output_section(q->data_shndx);
 583               q->needs_special_offset_handling =
 584                       (*p)->is_output_section_offset_invalid(q->data_shndx);
 585             }
 586         }
 587     }
 588
 589   // We have to support the case of not seeing any input objects, and
 590   // generate an empty file.  Existing builds depend on being able to
 591   // pass an empty archive to the linker and get an empty object file
 592   // out.  In order to do this we need to use a default target.
 593   if (input_objects->number_of_input_objects() == 0
 594       && layout->incremental_base() == NULL)
 595     parameters_force_valid_target();
 596
 597   int thread_count = options.thread_count_middle();
 598   if (thread_count == 0)
 599     thread_count = std::max(2, input_objects->number_of_input_objects());
 600   workqueue->set_thread_count(thread_count);
 601
 602   // Now we have seen all the input files.
 603   const bool doing_static_link =
 604     (!input_objects->any_dynamic()
 605      && !parameters->options().output_is_position_independent());
 606   set_parameters_doing_static_link(doing_static_link);
 607   if (!doing_static_link && options.is_static())
 608     {
 609       // We print out just the first .so we see; there may be others.
 610       gold_assert(input_objects->dynobj_begin() != input_objects->dynobj_end());
 611       gold_error(_("cannot mix -static with dynamic object %s"),
 612                  (*input_objects->dynobj_begin())->name().c_str());
 613     }
 614   if (!doing_static_link && parameters->options().relocatable())
 615     gold_fatal(_("cannot mix -r with dynamic object %s"),
 616                (*input_objects->dynobj_begin())->name().c_str());
 617   if (!doing_static_link
 618       && options.oformat_enum() != General_options::OBJECT_FORMAT_ELF)
 619     gold_fatal(_("cannot use non-ELF output format with dynamic object %s"),
 620                (*input_objects->dynobj_begin())->name().c_str());
 621
 622   if (parameters->options().relocatable())
 623     {
 624       Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 625       if (p != input_objects->relobj_end())
 626         {
 627           bool uses_split_stack = (*p)->uses_split_stack();
 628           for (++p; p != input_objects->relobj_end(); ++p)
 629             {
 630               if ((*p)->uses_split_stack() != uses_split_stack)
 631                 gold_fatal(_("cannot mix split-stack '%s' and "
 632                              "non-split-stack '%s' when using -r"),
 633                            (*input_objects->relobj_begin())->name().c_str(),
 634                            (*p)->name().c_str());
 635             }
 636         }
 637     }
 638
 639   // For incremental updates, record the existing GOT and PLT entries,
 640   // and the COPY relocations.
 641   if (parameters->incremental_update())
 642     {
 643       Incremental_binary* ibase = layout->incremental_base();
 644       ibase->process_got_plt(symtab, layout);
 645       ibase->emit_copy_relocs(symtab);
 646     }
 647
 648   if (is_debugging_enabled(DEBUG_SCRIPT))
 649     layout->script_options()->print(stderr);
 650
 651   // For each dynamic object, record whether we've seen all the
 652   // dynamic objects that it depends upon.
 653   input_objects->check_dynamic_dependencies();
 654
 655   // Do the --no-undefined-version check.
 656   if (!parameters->options().undefined_version())
 657     {
 658       Script_options* so = layout->script_options();
 659       so->version_script_info()->check_unmatched_names(symtab);
 660     }
 661
 662   // Create any automatic note sections.
 663   layout->create_notes();
 664
 665   // Create any output sections required by any linker script.
 666   layout->create_script_sections();
 667
 668   // Define some sections and symbols needed for a dynamic link.  This
 669   // handles some cases we want to see before we read the relocs.
 670   layout->create_initial_dynamic_sections(symtab);
 671
 672   // Define symbols from any linker scripts.
 673   layout->define_script_symbols(symtab);
 674
 675   // TODO(csilvers): figure out a more principled way to get the target
 676   Target* target = const_cast<Target*>(&parameters->target());
 677
 678   // Attach sections to segments.
 679   layout->attach_sections_to_segments(target);
 680
 681   if (!parameters->options().relocatable())
 682     {
 683       // Predefine standard symbols.
 684       define_standard_symbols(symtab, layout);
 685
 686       // Define __start and __stop symbols for output sections where
 687       // appropriate.
 688       layout->define_section_symbols(symtab);
 689
 690       // Define target-specific symbols.
 691       target->define_standard_symbols(symtab, layout);
 692     }
 693
 694   // Make sure we have symbols for any required group signatures.
 695   layout->define_group_signatures(symtab);
 696
 697   Task_token* this_blocker = NULL;
 698
 699   // Allocate common symbols.  We use a blocker to run this before the
 700   // Scan_relocs tasks, because it writes to the symbol table just as
 701   // they do.
 702   if (parameters->options().define_common())
 703     {
 704       this_blocker = new Task_token(true);
 705       this_blocker->add_blocker();
 706       workqueue->queue(new Allocate_commons_task(symtab, layout, mapfile,
 707                                                  this_blocker));
 708     }
 709
 710   // If doing garbage collection, the relocations have already been read.
 711   // Otherwise, read and scan the relocations.
 712   if (parameters->options().gc_sections()
 713       || parameters->options().icf_enabled())
 714     {
 715       for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 716            p != input_objects->relobj_end();
 717            ++p)
 718         {
 719           Task_token* next_blocker = new Task_token(true);
 720           next_blocker->add_blocker();
 721           workqueue->queue(new Scan_relocs(symtab, layout, *p,
 722                                            (*p)->get_relocs_data(),
 723                                            this_blocker, next_blocker));
 724           this_blocker = next_blocker;
 725         }
 726     }
 727   else
 728     {
 729       // Read the relocations of the input files.  We do this to find
 730       // which symbols are used by relocations which require a GOT and/or
 731       // a PLT entry, or a COPY reloc.  When we implement garbage
 732       // collection we will do it here by reading the relocations in a
 733       // breadth first search by references.
 734       //
 735       // We could also read the relocations during the first pass, and
 736       // mark symbols at that time.  That is how the old GNU linker works.
 737       // Doing that is more complex, since we may later decide to discard
 738       // some of the sections, and thus change our minds about the types
 739       // of references made to the symbols.
 740       for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 741            p != input_objects->relobj_end();
 742            ++p)
 743         {
 744           Task_token* next_blocker = new Task_token(true);
 745           next_blocker->add_blocker();
 746           workqueue->queue(new Read_relocs(symtab, layout, *p, this_blocker,
 747                                            next_blocker));
 748           this_blocker = next_blocker;
 749         }
 750     }
 751
 752   if (this_blocker == NULL)
 753     {
 754       if (input_objects->number_of_relobjs() == 0)
 755         {
 756           // If we are given only archives in input, we have no regular
 757           // objects and THIS_BLOCKER is NULL here.  Create a dummy
 758           // blocker here so that we can run the layout task immediately.
 759           this_blocker = new Task_token(true);
 760         }
 761       else
 762         {
 763           // If we failed to open any input files, it's possible for
 764           // THIS_BLOCKER to be NULL here.  There's no real point in
 765           // continuing if that happens.
 766           gold_assert(parameters->errors()->error_count() > 0);
 767           gold_exit(GOLD_ERR);
 768         }
 769     }
 770
 771   // When all those tasks are complete, we can start laying out the
 772   // output file.
 773   workqueue->queue(new Task_function(new Layout_task_runner(options,
 774                                                             input_objects,
 775                                                             symtab,
 776                                                             target,
 777                                                             layout,
 778                                                             mapfile),
 779                                      this_blocker,
 780                                      "Task_function Layout_task_runner"));
 781 }
 782
 783 // Queue up the final set of tasks.  This is called at the end of
 784 // Layout_task.
 785
 786 void
 787 queue_final_tasks(const General_options& options,
 788                   const Input_objects* input_objects,
 789                   const Symbol_table* symtab,
 790                   Layout* layout,
 791                   Workqueue* workqueue,
 792                   Output_file* of)
 793 {
 794   Timer* timer = parameters->timer();
 795   if (timer != NULL)
 796     timer->stamp(1);
 797
 798   int thread_count = options.thread_count_final();
 799   if (thread_count == 0)
 800     thread_count = std::max(2, input_objects->number_of_input_objects());
 801   workqueue->set_thread_count(thread_count);
 802
 803   bool any_postprocessing_sections = layout->any_postprocessing_sections();
 804
 805   // Use a blocker to wait until all the input sections have been
 806   // written out.
 807   Task_token* input_sections_blocker = NULL;
 808   if (!any_postprocessing_sections)
 809     {
 810       input_sections_blocker = new Task_token(true);
 811       // Write_symbols_task, Relocate_tasks.
 812       input_sections_blocker->add_blocker();
 813       input_sections_blocker->add_blockers(input_objects->number_of_relobjs());
 814     }
 815
 816   // Use a blocker to block any objects which have to wait for the
 817   // output sections to complete before they can apply relocations.
 818   Task_token* output_sections_blocker = new Task_token(true);
 819   output_sections_blocker->add_blocker();
 820
 821   // Use a blocker to block the final cleanup task.
 822   Task_token* final_blocker = new Task_token(true);
 823   // Write_symbols_task, Write_sections_task, Write_data_task,
 824   // Relocate_tasks.
 825   final_blocker->add_blockers(3);
 826   final_blocker->add_blockers(input_objects->number_of_relobjs());
 827   if (!any_postprocessing_sections)
 828     final_blocker->add_blocker();
 829
 830   // Queue a task to write out the symbol table.
 831   workqueue->queue(new Write_symbols_task(layout,
 832                                           symtab,
 833                                           input_objects,
 834                                           layout->sympool(),
 835                                           layout->dynpool(),
 836                                           of,
 837                                           final_blocker));
 838
 839   // Queue a task to write out the output sections.
 840   workqueue->queue(new Write_sections_task(layout, of, output_sections_blocker,
 841                                            input_sections_blocker,
 842                                            final_blocker));
 843
 844   // Queue a task to write out everything else.
 845   workqueue->queue(new Write_data_task(layout, symtab, of, final_blocker));
 846
 847   // Queue a task for each input object to relocate the sections and
 848   // write out the local symbols.
 849   for (Input_objects::Relobj_iterator p = input_objects->relobj_begin();
 850        p != input_objects->relobj_end();
 851        ++p)
 852     workqueue->queue(new Relocate_task(symtab, layout, *p, of,
 853                                        input_sections_blocker,
 854                                        output_sections_blocker,
 855                                        final_blocker));
 856
 857   // Queue a task to write out the output sections which depend on
 858   // input sections.  If there are any sections which require
 859   // postprocessing, then we need to do this last, since it may resize
 860   // the output file.
 861   if (!any_postprocessing_sections)
 862     {
 863       Task* t = new Write_after_input_sections_task(layout, of,
 864                                                     input_sections_blocker,
 865                                                     final_blocker);
 866       workqueue->queue(t);
 867     }
 868   else
 869     {
 870       Task_token* new_final_blocker = new Task_token(true);
 871       new_final_blocker->add_blocker();
 872       Task* t = new Write_after_input_sections_task(layout, of,
 873                                                     final_blocker,
 874                                                     new_final_blocker);
 875       workqueue->queue(t);
 876       final_blocker = new_final_blocker;
 877     }
 878
 879   // Create tasks for tree-style build ID computation, if necessary.
 880   final_blocker = layout->queue_build_id_tasks(workqueue, final_blocker, of);
 881
 882   // Queue a task to close the output file.  This will be blocked by
 883   // FINAL_BLOCKER.
 884   workqueue->queue(new Task_function(new Close_task_runner(&options, layout,
 885                                                            of),
 886                                      final_blocker,
 887                                      "Task_function Close_task_runner"));
 888 }
 889
 890 } // End namespace gold.